1. Field of the Invention
This invention relates to an imaging apparatus in which some of the pixels are used as elements for detecting phase differences to detect the focusing state, and relates also to a method for controlling the imaging apparatus.
2. Description of the Related Art
Japanese Patent No. 3592147, for example, proposes an imaging apparatus in which some of the pixels of the imaging element are used to detect the focusing state. In the imaging apparatus proposed in Japanese Patent No. 3592147, some of the pixels of the imaging element are set as phase-difference detecting pixels, the beams coming from an object through different pupil regions symmetric to the optical axis of the photographing lens are focused on a plurality of phase-difference detecting pixels, and the phase difference between these object beams is detected, ultimately detecting the focusing state of the photographing lens.
Each phase-difference detecting pixel is shielded from light, for example in one part, and receives only one of the light beams coming through the different pupil regions of the photographing lens. Consequently, the phase-difference detecting pixels are defective, and cannot be used to form an image. In the apparatus proposed in Japanese Patent No. 3592147, the signals output from the phase-difference detecting pixels are therefore interpolated by using the signals output from the adjacent pixels of the same color. If such interpolation is performed on an object of high spatial frequency, however, the image sharpness will decrease. In the imaging apparatus disclosed in Jpn. Pat. Appin. KOKAI Publication No. 2010-062640, the difference (in special frequency) between the output signals of the pixels surrounding any phase-difference detecting pixel is detected, and the ratio of the gain adjusting value to the interpolation correcting value is determined from the difference (in special frequency) detected.